Tumor cells exposed to a physiological matrix of type I collagen fibers form elongated collagenolytic invadopodia, which differ from dotty-like invadopodia forming on the gelatin substratum model. The related scaffold proteins, TKS5 and TKS4, are key components of the mechanism of invadopodia assembly. The molecular events through which TKS proteins direct collagenolytic invadopodia formation are poorly defined. Using coimmunoprecipitation experiments, identification of bound proteins by mass spectrometry, and in vitro pull-down experiments, we found an interaction between TKS5 and FGD1, a guanine nucleotide exchange factor for the Rho-GTPase CDC42, which is known for its role in the assembly of invadopodial actin core structure. A novel cell polarity network is uncovered comprising TKS5, FGD1, and CDC42, directing invadopodia formation and the polarization of MT1-MMP recycling compartments, required for invadopodia activity and invasion in a 3D collagen matrix. Additionally, our data unveil distinct signaling pathways involved in collagenolytic invadopodia formation downstream of TKS4 or TKS5 in breast cancer cells.

中文翻译：

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TKS5 和 FGD1/CDC42 信号级联的交叉点指导侵袭伪足的形成

暴露于I型胶原纤维生理基质的肿瘤细胞形成细长的溶胶原侵袭伪足，这与明胶基质模型上形成的点状侵袭伪足不同。相关的支架蛋白 TKS5 和 TKS4 是侵袭伪足组装机制的关键组成部分。TKS 蛋白指导溶胶原侵袭伪足形成的分子事件尚不清楚。通过免疫共沉淀实验、质谱鉴定结合蛋白以及体外下拉实验，我们发现 TKS5 和 FGD1 之间存在相互作用，FGD1 是 Rho-GTPase CDC42 的鸟嘌呤核苷酸交换因子，以其在组装中的作用而闻名侵入足肌动蛋白核心结构。发现了一种包含 TKS5、FGD1 和 CDC42 的新型细胞极性网络，可指导侵入伪足的形成和 MT1-MMP 回收区室的极化，这是侵入伪足活动和侵入 3D 胶原蛋白基质所需的。此外，我们的数据揭示了乳腺癌细胞中 TKS4 或 TKS5 下游溶胶原侵袭伪足形成所涉及的独特信号通路。